When the accurate positioning of changeable positions of machine components, such as multiple saws of a cutting machine, is to be undertaken and thereafter periodically observed until intentionally changed again, absolute linear position-displacement transducer systems are used. Each transducer has an external magnet, which is connected to a machine component, and when this machine component is moved, this external magnet moves along the wave guide, i.e. probe, of this transducer. For each machine component a separate transducer is used.
In respect to determining portions of movable components, in 1980 Messrs. Ueda and Noguchi in their U.S. Pat. No. 4,238,844, illustrated and discussed their displaced position detecting device. They determined the changed position of a component travelling or stopping between two fixed locations. A magnetostrictive wire extended between the two fixed locations, and the travelling component had an exciting means to generate an ultrasonic signal in the magnetostrictive wire, which was received in respective means located at each respective end of the magnetostrictive wire.
In 1982, Messrs Cullum, Thompson, and Worthington, in their U.S. Pat. No. 4,319,189 disclosed their magneto-acoustic position sensor, employing pulse code sequence generators and detectors and using a magnetostrictive wire. A position signalling electromagnetic drive head, could be moved with a machine component, and also moved along the magnetostrictive wire. When electrically pulsed, this drive head produced pulses which were received by detectors and analyzed to determine the position of the machine component.
In 1987 Messrs. Kataura and Ito in their U.S. Pat. No. 4,654,590, illustrated and described their method and apparatus for detecting the position of a movable object utilizing the magnetostrictive effect to generate ultrasonic waves. They placed several permanent magnets at equal spacings along a movable member, the position of which was to be determined from time to time. Then they used two permanent magnets spaced apart at a predetermined distance from each other and from the detection portion of a wave guide located alongside the movable member. When the wave guide system was energized, the magnetostrictive ultrasonic waves generated on the wave guide were detected at the positions of these permanent magnets, and the position of the movable member was detected from the number of ultrasonic wave signals and the propagation time.
Also in 1987, Messrs. Vennemann and Koninger in their U.S. Pat. No. 4,678,993, disclosed their distance measuring device operating with torsional ultrasonic waves detected without mode conversion. A permanent magnet moving in like relationship to a movable member, then moved along a tube of magnetostrictive material. When electrical pulses were produced by a pulse generator and these pulses travelled along the tube, then at the location of the permanent magnet torsional ultrasonic pulses were generated, and they served as position signals indicating the location of the movable member.
Although there have been many successful products, apparatuses, and methods, utilized by others, centering on the utilization of signal generation apparatus built around a tube made of magnetostrictive material, which experiences a local rotary strain where two magnetic fields interact, there remained a need to provide overall equipment at lower costs, when more movable members of machinery had to be controlled and/or monitored.